Understanding Histamine
While awareness of histamine intolerance is low, most people have heard of histamine (from antihistamines), even if they aren't quite able to explain what it is. Things start to fall into place when they realise that not all histamine is the same. Your body deals with two distinct types: internal and external.
- Internal (or endogenous) histamine is the histamine your own body produces. It’s a vital chemical messenger involved in your immune system, digestion, and nervous system. Your mast cells (a type of immune cell) release it in response to allergens, stress, injury, or hormonal changes
- External (or exogenous) histamine is the histamine you consume through your diet. It’s found in many common foods and drinks, particularly those that are aged, fermented, or cured. Think mature cheese, red wine, salami, and even leftovers
Both sources contribute to the total amount of histamine circulating in your body at any given time, filling up what we like to call your histamine bucket. Antihistamines, the type that people with hay fever might take, work to block your mast cells from releasing internal histamine. The second type, external histamine, is broken down by an enzyme called Diamine Oxidase, or DAO.
The Role of Diamine Oxidase (DAO)
So, what is DAO? In simple terms, diamine oxidase is an enzyme that is created in our gut. An enzyme is a type of protein that speeds up chemical reactions in your body. DAO’s specific job is to break down the histamine you ingest from food and drink.
Its location is critical to its function. DAO is primarily produced and found in the lining (the mucosa) of your small intestine. You can think of it as a dedicated gatekeeper, standing guard at the entrance to your bloodstream. When you eat a meal containing histamine, the DAO enzyme gets to work right there in your gut. It metabolises the histamine, converting it into an inactive compound that your body can easily and safely excrete. This entire process is designed to happen before the histamine has a chance to be absorbed through the intestinal wall and enter your system.
What Happens When DAO Can't Keep Up?
The system works beautifully when you have enough active DAO to handle the amount of histamine you're consuming. However, for many people, this isn't the case. A lack of sufficient enzyme activity is known as DAO deficiency, and research suggests it may be a factor in a significant number of histamine intolerance cases.
When your DAO levels are low, or when you consume a particularly high-histamine meal, your natural supply of the enzyme can become overwhelmed. It simply can’t break down all the incoming dietary histamine quickly enough. What happens to the excess? It bypasses the gatekeeper and gets absorbed through your gut lining into your bloodstream. This is where the two types of histamine meet, and where the popular “histamine bucket” analogy becomes so useful.
The Histamine Bucket: Where External and Internal Histamine Meet
Imagine your body has a bucket that can hold a certain amount of histamine. The size of this bucket is unique to you. The water already in the bucket represents your baseline level of internal histamine, produced by your own body in response to daily stressors, allergens, or hormonal fluctuations.
On a good day, your bucket might be only slightly full. On a day when you’re dealing with seasonal allergies or feeling particularly stressed, it might be much fuller. When undigested external histamine from your food is absorbed into your bloodstream, it's like pouring an extra jug of water into that bucket. If the bucket was already near the top, this extra load from your meal can cause it to overflow. It’s this overflow, when your total histamine load exceeds your body's capacity to break it down, that is thought to lead to histamine-related reactions.
This explains why your tolerance can vary from day to day. A meal that causes no issues one week might be problematic the next, simply because the starting level of histamine in your bucket was higher. You don't have to be histamine intolerant to experience these reactions either - many people without histamine intolerance might occasionally experience a snuffly nose after drinking a couple of glasses of red wine, especially on a hot or stressful day.
How DAO Supplementation Supports Your Body's Natural Process
Understanding the DAO mechanism helps clarify why DAO supplements are designed to be taken in a specific way. The goal of supplementation is not to affect the internal histamine already in your bucket. Instead, it is to support the initial breakdown of external, dietary histamine right where it happens: in your gut.
This is why DAO supplements are taken shortly before a meal. The aim is to ensure a sufficient amount of the enzyme is present in your small intestine, ready to greet the histamine from your food as it arrives. It works alongside your body’s own DAO to help metabolise dietary histamine before it has a chance to be absorbed.
It is possible to make up for a lack of natural DAO by taking DAO supplements. For instance, our supplement Aperitif is designed to be taken 15 to 20 minutes before ingesting histamine-rich food or drink. This timing allows the enzyme to be in the right place at the right time to assist with the digestion of histamine from your meal.
It’s important to remember that this is a different mechanism from antihistamine medications. Antihistamines work systemically (throughout your body) by blocking histamine receptors, which can help manage the effects of internal histamine. DAO works locally (in your gut) on external histamine from your diet.
A Holistic Approach to Your Histamine Journey
Managing histamine intolerance is a personal journey. While supporting your DAO levels can be an important tool, it's part of a bigger picture. Identifying your personal triggers is a crucial step. This is often done through a temporary, supervised low-histamine diet, which should always be undertaken with the guidance of a qualified professional.
We strongly encourage you to work with a registered dietitian or healthcare provider who specialises in histamine intolerance. They can help you create a personalised plan that works for you. You can find a list of practitioners we know and trust on our About page. Understanding how your body works is the first step towards feeling empowered and in control of your health.